Electric firing circuit for explosive charges



July 26, 1966 M. M CARTY 3,262,338

ELECTRIC FIRING CIRCUIT FOR EXPLOSIVE CHARGES Filed. April 24, 1964 FROM RECEIVER 12 POLAR ITY REVERSAL SWITCH Fig. 2

INVENTOR ALBERT M. McCARTY ATTORNEY United States Patent Navy Filed Apr. 24, 1964, Ser. No. 362,535 6 Claims. (Cl. 10218) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to electric firing circuits, and more particularly to an electric firing circuit capable of selectively detonating a plurality of explosive charges by remotely generated command signals.

Underwater sound technology, especially as it relates to antisubmarine warfare, has developed a need for a repeatable sound source at selected ocean depths. Explosive charges have been found well-suited for generating the sound, however, heretofore known systems for selectively firing the charges by remotely generated command signals have not been entirely satisfactory. For example, one prior art system utilizes a stepping relay which, on a command signal, sequentially connects the firing circuit of each explosive to an electrical power supply. As in any switching operation, factors of cost and reliability are indeed important considerations. In antisubmarine warfare, where most of the sonar equipment must be designed for carrying in an aircraft, weight and space are additional factors not to be overlooked. The mechanical switching type firing circuits have not met all of these requirements, especially in the strict sense demand for antisubmarine missions.

It is therefore an object of the present invention to provide an electric firing circuit for a plurality of explosive charges remotely operated by a command signal, in which the charges are selectively detonated, and in which a common electrical connector is utilized between the explosive charges and a command signal-responsive actuator.

Another object of the invention is to provide an electric firing circuit which is especially suitable for use in an underwater explosive sound source of the type launched from an aircraft for use in anti-submarine warfare, in which the circuit adds little additional weight and space to airborne equipment, and which is capable of withstanding the high accelerations usually encountered by aircraft launched sonar equipment.

Still another object of the invention is to provide an electric firing circuit capable of operating at deep water depths, which is inexpensive to manufacture, and simple to operate, and which is safe and reliable under ordinary use.

Various other objects and advantages will appear from the following description of one embodiment of the invention, and the most novel features will be particularly pointed out hereinafter in connection with the appended claims.

One embodiment of the present invention contemplates an electric firing circuit, especially suitable for use with an underwater explosive sound source buoy, permits a plurality of explosive charges to be selectively fired by a radio signal. A signal responsive command actuator connects to a novel arrangement of diodes, frangible shunts and resistances through a common input connection. The actuator applies a DC. (direct current) voltage to the common input in either a positive or negative polarity. Each time the polarity changes, a charge is fired, and another charge is armed.

In the drawing:

FIG. 1 pictorially represents an elevation view of one embodiment of the invention as applied. to an underwater explosive sound source buoy; and

FIG. 2 represents a schematic diagram of an electric firing circuit of the embodiment shown in FIG. 1.

The illustrated embodiment of the invention, FIG. 1 shows an operationally ready underwater explosive sound source buoy comprising a flotation cannister 10 resting at the surface of a body of water. An antenna 11 extending from the top of the cann-ister 10 connects to a radio receiver '12, shown in dotted outline, contained therein. A plurality of explosive charges 13, '14, 15 and 16 depend at selected depths from the bottom of the cannister 10 by a cable 18. Of course the charges 13, 14, 15 and 16 must be separated from each other along the length of the cable 18 a sufiicient distance that the explosion of one charge will not detonate an adjacent charge. A command actuator 20, also shown in dotted outline, has an input operatively connected through a conductor 19 to the output of the receiver 12 and provides thereby selective reversing of polarity from a DC. power supply to a common electrical conductor in the cable 18 for firing the charges 13, :14, .15 and 16 in a manner herein described.

Referring now to FIG. 2, the command actuator 20 is shown as comprising a multivibrator having one input connected to the conductor 19 and two outputs connected by conductors 22 and 23 to control. inputs of a polarity reversing switch 24. The multivibrator 2 1 is of the bistable type so that it alternately produces a voltage on conductors 22 and 23 for each pulse from the receiver output. The polarity reversing switch 24 also includes two power input terminals respectively connected to the positive and negative terminals of a battery 26, and two power output terminals respectively connected to conductors 27 and 28 in the cable 18. Conductor Z7 is connected to a grounded shielding of the cable '18. The power output terminals are switched in polarity each time the control input terminals sense a shift in the outputs of the multivibrator 21. Such switch may, for example, comprise silicone controlled rectifiers or other semiconductor devices connected for polarity reversal operation in response to the control inputs on conductors 22 and'23. The command actuator 20 may also be constructed in various other ways using state of the art techniques without departing from the fundamental inventive concepts.

At the charge-connected end of the cable 18, conductor 28 divides into fourparallel conductors 31, 32, 33 and 34 which form the electrical connections to four parallel detonating circuits in the charges 113, 14, 15 and 16. The other end of each detonating circuit is connected to ground through a common conductor 36.

The detonating circuit of the charge 13 comprises a diode 37a, and a detonating resistor or element 38a serially connected between the conductors 31 and 36. A frangible shunt 41a, imbedded in the charge 13 provides an arming circuit for the detonating circuit of the charge 14. The diode 37a is connected so as to offer a relatively low resistance to current flow when a positive voltage is applied on the conductor 31, and conversely a relatively high resistance when the voltage is negative.

The detonating circuit of the charge 14 comprises a diode 37b, detonating resistance 38b, and current limiting resistor 42b serially connected between the conductors 32 and 36. The frangible shunt 41a of the charge 13 is electrically connected across the resistance 38b by conductors 43 and 44. The diode 37b is connected opposite in polarity from the diode 37a. That is, it passes current when the conductor 32 is positive. A frangible shunt 3 41b, imbedded in the charge 14 provides an arming circuit for the detonating circuit of the charge 15.

The detonating circuits of the charges 15 and 16 include diodes 37c and 37d, detonating resistances 38c and 38d, and current limiting resistors 42c and 42d serially connected in the same manner as corresponding elements of the charge 14 except that the diodes 37c and 37d are respectively connected to pass current when conductor 33 is positive and conductor 34 is negative. The frangible shunt 41b is connected across the resistance 380 by conductors 46 and 47 in the cable 18; and a frangible shunt 410 is imbedded in the charge 15 and connected across the resistance 38d by conductors 48 and 49 in the cable 18.

The resistors 42b, 42c and 42d are of high enough resistance to insure a voltage drop between the conductors 28 and 36 sufiicient to fire each charge but still to permit enough current through a dc-shunted detonating resistance to detonate its charge.

Operation of the electric firing circuit of the present invention should now be apparent. In the ready state, the polarity reversing switch 24 causes the conductor 28 to be negative. Diodes 37b and 37d will pass only a small current through frangible shunts 41a and 41c and resistors 42b and 42d, and there is no current through diodes 37a and 370. On receipt of a command signal of a particular frequency or bandwidth by the receiver 12, a pulse to the multivibrator 21 causes the polarity reversing switch 24 to reverse the polarity at its output. Thus, conductor 28 becomes positive and diodes 37a and 37c conduct. The

' shunt 41b and resistor 42c prevent firing of the charge 15,

and diodes 37b and 37d prevent firing of the charges 14 and 16. However, sufficient current passes through the diode 37a and resistance 38a to cause detonation of the charge 13. The explosion produced thereby opens the frangible shunt 41a thereby arming the charge 14. A second command signal received by the receiver 12 will produce another pulse to the multivibrator 21 reversing the polarity so that the conductor 28 again becomes negative. The shunt 41c prevents firing of the charge 16 and the diode 37c prevents charge 15 from firing; but suflicient current passes through the diode 37 b and resistances 38b and 42b to detonate the charge 14. Again, the explosion produced thereby will open the frangible shunt 41b to arm the detonating circuit of the charge 15.

It should now be obvious that two subsequent reversals in polarity will similarly detonate charges 15 and 16. It should also be obvious that the number of charges and detonating circuits is not limited to the four illustrated. A limiting factor as to the number of circuits will be the minimum current required through the first-fired detonating circuit. This, of course, is a function of the applied voltage and resistance of the first-fired circuit relative to the other parallel detonating circuits.

Some of the many advantages of the present invention should now be apparent. For example, mechanical type sequential selector switches have been eliminated, the electrical elements required admit of smaller, lightweight packaging, the invention is more reliable and less expensive than the prior art devices. Further, the invention is particularly suitable for use in underwater sound source buoys launched from aircraft.

It will be understood that various changes in the dehave been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. An electric firing circuit for selectively firing a plurality of explosive charges, comprising:

actuator means responsive to a command signal for producing a reversing polarity DC. voltage at the output thereof;

a plurality of parallel detonating circuits having their common connections connected to the output of said actuator means, each of said detonating circuits having a detonating element operatively connected to a one of the explosive charges; and

frangible arming means operatively connected between adjacent detonating circuits and in shunt relation with said detonating element, said frangible arming means providing a low impedance electrical path across said detonating element.

2. An electric firing circuit as recited in claim 1 wherein each of said detonating circuits comprises:

a diode electrically connected in series with said detonating element, said diodes of adjacent detonating circuits being connected in opposed polarity relationship.

3. An electric firing circuit as recited in claim 2 wherein said frangible arming means is embedded in the charge of an adjacent detonating circuit.

4. An electric firing circuit as recited in claim 3 wherein each of said detonating circuits further comprises:

a resistor connected. in series with said diode and said detonating element.

5. An electric firing apparatus as recited in claim 4 wherein said actuator means comprises:

a polarity reversal means having a control input forming the input to said actuator means, a DC. power input, and an output forming the output from said actuator means.

6. An electric firing circuit as recited in claim 5 further comprising:

a flotation canister housing said actuator means;

radio receiver means contained in said housing having an output connected to the input of said actuator means;

cable means depending from said housing to said detonating circuits for conducting electrical signals from said actuator means to said detonating circuits.

References Cited by the Examiner UNITED STATES PATENTS 2,411,787 12/ 1946 Hammond 102--8 2,599,245 6/l952 Finn 102-21 X 2,871,784 2/1959 Balir l0221.6 X 3,010,396 11/1961 Coleman 1022l.6 3,086,465 4/1963 Montfort 10222 3,170,399 2/1965 Hinman 102l9.2

BENJAMIN A. BORCHELT, Primary Examiner. FRED C. MATTERN, 111., Examiner.

V, R. PENDEGRASS, Assistant Examiner. 

1. AN ELECTRIC FIRING CIRCUIT FOR SELECTIVELY FIRING A PLURALITY OF EXPLOSIVE CHARGES, COMPRISING: ACTUATOR MEANS RESPONSIVE TO A COMMAND SIGNAL FOR PRODUCING A REVERSING POLARITY D.C. VOLTAGE AT THE OUTPUT THEREOF; A PLURALITY OF PARALLEL DETONATING CIRCUITS HAVING THEIR COMMON CONNECTIONS CONNECTED TO THE OUTPUT OF SAID ACTUATOR MEANS, EACH OF SAID DETONATING CIRCUITS HAVING A DETONATING ELEMENT OPERATIVELY CONNECTED TO ONE OF THE EXPLOSIVE CHARGES; AND FRANGIBLE ARMING MEANS OPERATIVELY CONNECTED BETWEEN ADJACENT DETONATING CIRCUITS ARE IN SHUNT RELATION WITH SAID DETONATING ELEMENT, SAID FRANGIBLE ARMING MEANS PROVIDING A LOW IMPEDANCE ELECTRICAL PATH ACROSS SAID DETONATING ELEMENT. 